1. Technical Field
This disclosure relates generally to apparatus and methods for implant insertion. More particularly, to apparatus and methods for insertion of implants to facilitate fusion of adjacent bony structure.
2. Background of the Related Art
A large number of orthopedic procedures involve the insertion of either natural or prosthetic implants into bone or associated tissues. These procedures include, for example, ligament repair, joint repair or replacement, non-union fractures, facial reconstruction, spinal stabilization and spinal fusion. In a typical procedure, an insert, dowel or screw is inserted into a prepared bore formed in the bone or tissues to facilitate repair and healing. See, for example, U.S. Pat. Nos.: 5,470,334 to Ross et al.; 5,454,811 to Huebner, 5,480,403 to Lee et al.; 5,40,805 to Warren; 5,358,511 to Gatturna et al.; and 4,877,020 to Vich.
Some implants are particularly configured with cavities and bores to facilitate bony ingrowth and enhance anchoring of the implant at the insertion site. See, for example, U.S. Pat. Nos.: 4,328,593 to Sutter et al.; 4,936,851 to Fox et al.; and 4,878,915 to Brantigan. Implants in the form of fusion cages having internal cavities to receive bone growth stimulation materials such as bone chips and fragments are disclosed, for example, in U.S. Pat. Nos.: 4,501,269 to Bagby; 4,961,740 to Ray et al.; 5,015,247 to Michaelson; and 5,489,307 to Kuslich et al. These types of implants are particularly well suited for intervertebral spinal fusion procedures necessitated by injury, disease or some degenerative disorder of the spinal disc. Subsequently, there may be progressive degeneration leading to mechanical instability between adjacent vertebrae necessitating direct fusion of the vertebrae while maintaining a pre-defined intervertebral space. This fusion may be accomplished by the insertion of one or more of the specialized implants as discussed above and also discussed in commonly assigned U.S. Pat. No. 5,026,373, incorporated herein by reference.
Both anterior (transabdominal) and posterior surgical approaches are used for interbody fusions of the lumbar spine. Fusions in the cervical area of the spine are primarily done using an anterior approach. Typically, an implant such as a plug, dowel prosthesis or cage is inserted into a preformed cavity inside the interbody, interdiscal space. Since it is desirable in these procedures to promote a "bone to bone" bridge, connective tissue and at least a portion of the discal tissue is removed. Preferably, relatively deep cuts are made in the adjacent bones in order to penetrate into the softer, more vascularized cancerous region to facilitate bone growth across the implant.
When installing these specialized implants, an insertion tool is used to position the implant in the desired intervertebral location. See, for example, U.S. Pat. Nos.: 3,848,601 to Ma et al.; 4,501,269 to Bagby; 4,877,020 to Vich; and 4,878,915 to Brantigan. Once in position, the insertion tool is removed and, where the implant structure permits, bone chips or other bone growth inducing substances are packed into the implant in vivo. Subsequently, an end cap or other sealing structure is positioned to close the implant. See, for example, commonly assigned U.S. Pat. No. 4,961,740 to Ray et al. incorporated herein by reference.
Typical insertion tools use either a single implant engagement structure or, at most, two implant engagement structures to facilitate positioning of the implant. For example, in U.S. Pat. No. 4,501,269 to Bagby, prongs are used to engage the implant. In U.S. Pat. Nos. 4,878,915 to Brantigan and 5,015,247 to Michaelson, a threaded rod and slot are used to engage the implant. In U.S. Pat. Nos.: 4,961,740 to Ray et al.; 5,489,308 and 5,489,307, both to Kuslich et al.; and 4,936,838 to Bagby, a single central shaft is used. In all of these insertion tools, no structure is provided to permit the insertion tool to attach to an outer peripheral portion of the implant, either in vitro or in vivo. Further, these tools do not provide structure which separately engages both the implant and the implant closure, e.g. an end cap.
Accordingly, a need exists for an insertion tool which is capable of either inserting an implant preloaded with bone chips, etc. Such in vitro packing facilitates the surgical procedure because it is often time consuming and relatively difficult, especially for example in cervical applications, to pack the cage in vivo. It would also be advantageous if such insertion tool could be additionally used to insert/position an empty implant for subsequent in vivo packing and closure.